This invention relates in general to a remote control arrangement as disclosed in related U.S. application Ser. No. 933,014, filed 11 Aug. 1978, and more particularly to a remote control arrangement with a prepulse having a three fold pulse width before the start pulse.
A remote control arrangement is known in principle from German Published patent application No. 2,503,083, where it is used for infrared remote control.
Apart from these known remote control techniques which are based on the principle of pulse-code modulation, remote control techniques are known in which the individual commands are characterized by signals whose frequencies differ by a constant amount. Such remote control techniques are used particularly for ultrasonic remote control, cf., for example, the periodical "radio mentor electronic", 1975, pages 347 to 349. From that prior art it is known that both the oscillator serving as the time base for the transmitter and the oscillator serving as the time base for the receiver are crystal oscillators, i.e., both oscillators have a small relative frequency change. It is also known from that prior art to provide in the receiver a check circuit for the period of the received ultrasound signal, whereby interfering frequencies outside the frequency band occupied by the signal frequencies can be eliminated.
Since the compulsion to use two crystal oscillators in a remote control arrangement involves relatively great expense, even taking into account that use can be made of chrominance-subcarrier crystals, which are relatively low in cost because they are mass-produced, the object of the main application is to improve a remote control arrangement so as to eliminate the above-mentioned compulsion and nevertheless permit safe and simple interference- and error-pulse detection and suppression.